This "first-light" image from KCWI (middle) shows more than 100 stars in the core of the globular cluster Messier 3 (right). The boxes are positioned around some of the stars, and connect to their corresponding spectra. The green outlines showcase the highest spectral-resolution setting of KCWI. Each star has a rich spectrum of absorption lines (the dips) that contain information about the velocity and chemical composition of the star.

Keck Cosmic Web Imager Achieves "First Light"

A Caltech-built instrument designed to study the mysteries of the cosmic web—streams of gas connecting galaxies—has captured its first image, an event astronomers call "first light." The instrument, called the Keck Cosmic Web Imager, or KCWI, was recently installed on the W. M. Keck Observatory in Hawaii.

KCWI captures highly detailed spectral images of cosmic objects to reveal their temperature, motion, density, mass, distance, chemical composition, and more. The instrument is designed to study the wispy cosmic web; it will also observe many other astronomical phenomena, including young stars, evolved stars, supernovas, star clusters, and galaxies.

"I'm incredibly excited. These moments happen only a few times in one's life as a scientist," says principal investigator Christopher Martin, professor of physics at Caltech. "To take a powerful new instrument, a tool for looking at the universe in a completely novel way, and install it at the greatest observatory in the world is a dream for an astronomer. This is one of the best days of my life."

Martin and his Caltech team, in collaboration with scientists at UC Santa Cruz and with industrial partners, designed and built the 5-ton instrument—about the size of an ice cream truck. It was then shipped from California to Hawaii on January 12. Since then, Keck Observatory's team has been working diligently to install and test KCWI on Keck II, one of the twin 10-meter Keck Observatory telescopes.

"KCWI will really raise the bar in terms of Keck Observatory's capabilities," says Anne Kinney, chief scientist at Keck Observatory. "I think it will become the most popular instrument we have, because it will be able to do a great breadth of science, increasing our ability to understand and untangle the effects of dark matter in galaxy formation."

The W. M. Keck Observatory is a private 501(c)3 nonprofit organization and a scientific partnership of Caltech, the University of California, and NASA.